A Russian deputy gestures during the session of the Duma in Moscow. (Reuters)

Moscow, Oct. 22 (Reuters): Russia's lower house of parliament ratified the Kyoto Protocol today, clearing the way for the long-delayed climate change pact to come into force worldwide.

The UN accord aimed at battling global warming is already backed by 126 countries, but it needed Russia's support to make it internationally binding after the US, the world's biggest polluter, pulled out in 2001.

The 1997 Kyoto Protocol obliges rich nations to cut overall emissions of heat-trapping carbon dioxide by 5.2 per cent below 1990 levels by 2008-12 by curbing use of coal, oil and natural gas and shifting to cleaner energies like solar or wind power.

'The entry into force of Kyoto is the biggest step forward in environmental politics and law we have ever seen,' said Jennifer Morgan, director of the WWF conservation group's climate change programme.

To come into force, the pact needed to be ratified by countries accounting for at least 55 per cent of developed nations' greenhouse gas emissions.

Russia, which accounts for 17 per cent, became the key to Kyoto after the US pull out.

Washington said the pact was too costly and unfairly exempted large rapidly industrialising countries such as China and India.

But EU Commission President Romano Prodi said Russia's backing would put additional pressure on the US to reconsider its position.

'The Kyoto Protocol may not be perfect but it is the only effective tool that is available to the international community,' he said in a statement.

'The United States should not abstain from the one fight that is crucial for the future of mankind.'

Russia's Duma passed the Kyoto bill by 334 votes in favour, with 73 against and two abstentions. The Upper house will consider Kyoto on October 27, Interfax news agency said. After that it will go to President Vladimir Putin who will have up to two weeks to sign it.

These steps are seen as formalities after today's vote in the Duma, which is controlled by pro-Kremlin parties.

Klaus Toepfer, executive director of the UN Environment Programme (UNEP), said the decision would help concentrate global efforts on meeting Kyoto's targets.

But he added that 'the goal of stabilising the climate and securing the stability of the planet is however a long way off'.

Rising global temperatures have been linked to extreme weather including droughts, flooding and higher sea levels, which some see as possible sparks for regional conflicts.

Russia signed the Protocol in 1999. But it only signalled it would ratify it this year in exchange for EU agreement on the terms of Moscow's admission to the World Trade Organisation.